Wireless power transmitter and receiver

ABSTRACT

A method in which a power transmitter comprising multi coils transmits wireless power, includes detecting a second power receiver while transmitting power to a first power receiver, determining at least one primary coil appropriate for power transmission, determining whether the second power receiver supports a shared mode protocol using the determined at least one primary coil, and transmitting, if the second power receiver supports a shared mode protocol, power to the first and second power receivers according to the shared mode protocol, wherein the shared mode protocol is a protocol that simultaneously manages information exchange between the power transmitter and a plurality of power receivers.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a Continuation of U.S. patent application Ser. No.15/554,876 filed on Aug. 31, 2017, which is the National Phase ofPCT/KR2016/001873 filed on Feb. 25, 2016, which claims priority under 35U.S.C. § 119(e) to U.S. Provisional Application No. 62/127,847 filed onMar. 4, 2015, all of these applications are hereby expresslyincorporated by reference into the present application.

BACKGROUND OF THE INVENTION Field of the Invention

The present invention relates to a wireless power transmitter andreceiver and a method of controlling the same.

Discussion of the Related Art

A contactless wireless charging method is an energy transfer method forelectromagnetically transferring energy without using a wire in a methodfor sending energy through an existing wire so that the energy is usedas power for an electronic device. The contactless wireless transmissionmethod includes an electromagnetic induction method and a resonantmethod. In the electromagnetic induction method, a power transmissionunit generates a magnetic field through a power transmission coil (i.e.,a primary coil), and a power reception coil (i.e., a secondary coil) isplaced at the location where an electric current may be induced so thatpower is transferred. In the resonant method, energy is transmittedusing a resonant phenomenon between the transmission coil and thereception coil. In this case, a system is configured so that the primarycoil and the secondary coil have the same resonant frequency, andresonant mode energy coupling between the transmission and receptioncoils is used.

SUMMARY OF THE INVENTION

The present invention provides operation of a power transmitter thatflexibly adjusts a power amount transmitting to each power receiveraccording to a change in the number of charging power receivers.

In accordance with an aspect of the present invention, a method in whicha power transmitter including multi coils transmits wireless powerincludes: detecting a second power receiver while transmitting power toa first power receiver; determining at least one primary coilappropriate for power transmission; determining whether the second powerreceiver supports a shared mode protocol using the determined at leastone primary coil; and transmitting, if the second power receiversupports the shared mode protocol, power to the first and second powerreceivers according to the shared mode protocol, wherein the shared modeprotocol is a protocol that simultaneously manages information exchangebetween the power transmitter and a plurality of power receivers.

Further, the determining of whether the second power receiver supportsthe shared mode protocol may include receiving a configuration packetfrom the second power receiver; and determining whether the second powerreceiver supports the shared mode protocol through a mode field includedin the configuration packet.

Further, the determining of whether the second power receiver supportsthe shared mode protocol through the mode field may include determiningthat the second power receiver supports the shared mode protocol whenthe mode field is set to ‘1’, and determining that the second powerreceiver does not support the shared mode protocol when the mode fieldis set to ‘0’.

Further, if the second power receiver supports the shared mode protocol,the method may further include starting power transmission to the secondpower receiver at a start time point of a next slotted frame.

Further, if the second power receiver does not support the shared modeprotocol, the method may further include not transmitting power to thesecond power receiver until the power transmitter is prepared to servethe second power receiver in an exclusive mode, wherein the exclusivemode may be a mode that serves one power receiver at one time.

Also, in accordance with another aspect of the present invention, amethod in which a power receiver receives wireless power includes: beingdetected by a power transmitter transmitting power to another powerreceiver; transmitting a configuration packet indicating whether thepower receiver supports a shared mode protocol to the power transmitter;and detecting, if the power receiver supports the shared mode protocol,Frequency Shift Keying (FSK) in a power signal received from the powertransmitter and participating in power transmission of the powertransmitter together with the another power receiver according to theshared mode protocol, wherein the shared mode protocol is a protocolthat simultaneously manages information exchange between the powertransmitter and a plurality of power receivers.

Further, a mode field included in the configuration packet may indicatewhether the power receiver supports the shared mode protocol.

Further, when the mode field is set to ‘1’, the mode field may indicatethat the power receiver supports the shared mode protocol, and when themode field is set to ‘0’, the mode field may indicate that the powerreceiver does not support the shared mode protocol.

Further, if the power receiver supports the shared mode protocol, themethod may further include starting power reception from the powertransmitter at a start time point of a next slotted frame.

Further, if the power receiver does not support the shared modeprotocol, the method may further include not receiving power from thepower transmitter until the power transmitter is prepared to serve thepower receiver in an exclusive mode, wherein the exclusive mode is amode in which the power transmitter serves one power receiver at onetime.

Also, in accordance with another aspect of the present invention, apower transmitter includes a coil assembly including multi coils; aninverter that converts a DC signal to an AC signal; a tank circuit thatprovides impedance matching; a communication unit that performscommunication with a power receiver; and a control unit that controlspower transfer, wherein the power transmitter detects a second powerreceiver while transmitting power to a first power receiver, determinesat least one primary coil appropriate for power transmission, determineswhether the second power receiver supports a shared mode protocol usingthe determined at least one primary coil, and transmits power to thefirst and second power receivers according to the shared mode protocolwhen the second power receiver supports the shared mode protocol,wherein the shared mode protocol is a protocol that simultaneouslymanages information exchange between the power transmitter and aplurality of power receivers.

Further, the power transmitter may receive a configuration packet fromthe second power receiver and determine whether the second powerreceiver supports the shared mode protocol through a mode field includedin the configuration packet.

Further, when the mode field is set to ‘1’, the power transmitter maydetermine that the second power receiver supports the shared modeprotocol, and when the mode field is set to ‘0’, the power transmittermay determine that the second power receiver does not support the sharedmode protocol.

Further, when the second power receiver supports the shared modeprotocol, the power transmitter may start power transmission to thesecond power receiver at a start time point of a next slotted frame.

Further, when the second power receiver does not support the sharedmode, the power transmitter may not transmit power to the second powerreceiver until the power transmitter is prepared to serve the secondpower receiver in an exclusive mode, and the exclusive mode may be amode that serves one power receiver at one time.

Also, in accordance with another aspect of the present invention, apower receiver includes: a coil assembly including multi coils; a powerconverter that converts AC power to a voltage and a current appropriatefor a load circuit; a tank circuit that provides impedance matching; acommunication unit that performs communication with a power receiver;and a control unit that controls power transfer, wherein the powerreceiver is detected by a power transmitter transmitting power toanother power receiver, transmits a configuration packet indicatingwhether the power receiver supports a shared mode protocol to the powertransmitter, when the power receiver supports the shared mode protocol,detects Frequency Shift Keying (FSK) in a power signal received from thepower transmitter, and participates in power transmission of the powertransmitter together with the another power receiver according to theshared mode protocol, wherein the shared mode protocol is a protocolthat simultaneously manages information exchange between the powertransmitter and a plurality of power receivers.

Further, a mode field included in the configuration packet may indicatewhether the power receiver supports the shared mode protocol.

Further, when the mode field is set to ‘1’, the mode field may indicatethat the power receiver supports the shared mode protocol, and when themode field is set to ‘0’, the mode field may indicate that the powerreceiver does not support the shared mode protocol.

Further, when the power receiver supports the shared mode protocol, thepower receiver may start power reception from the power transmitter at astart time point of a next slotted frame.

Further, when the power receiver does not support the shared modeprotocol, the power receiver may not receive power from the powertransmitter until the power transmitter is prepared to serve the powerreceiver in an exclusive mode, and wherein the exclusive mode may be amode in which the power transmitter serves one power receiver at onetime.

According to an embodiment of the present invention, while a powertransmitter transmits power, even if a new power receiver participatesin charge, the power transmitter can let the new power receiver beparticipated in power transmission effectively without disturbing powertransmission to an already charging power receiver.

Further, according to an embodiment of the present invention, a powerreceiver operating in an exclusive mode among a plurality of powerreceivers operating in a shared mode can be detected.

In addition, various effects according to an embodiment of the presentinvention will be described in detail hereinafter.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagram illustrating an embodiment of various electronicdevices in which a wireless charge system is introduced.

FIG. 2 is a block diagram of a wireless power transmitting/receivingsystem according to an embodiment of the present invention.

FIG. 3 is a block diagram of a power transmitting equipment according toan embodiment of the present invention.

FIG. 4 is a block diagram of a power receiving equipment according to anembodiment of the present invention.

FIG. 5 is a diagram illustrating an operating mode of a wireless powertransmitting/receiving system according to an embodiment of the presentinvention.

FIG. 6 is a state diagram of a wireless power transmitter in anexclusive mode.

FIG. 7 is a diagram illustrating a power transfer control method in anexclusive mode.

FIG. 8 is a state diagram of a power receiver in a shared mode.

FIG. 9 is a diagram illustrating a frame structure for datacommunication.

FIG. 10 is a diagram illustrating a format of a sync pattern accordingto an embodiment of the present invention.

FIG. 11 is a diagram illustrating a configuration packet according to afirst embodiment of the present invention.

FIG. 12 is a diagram illustrating a configuration packet according to asecond embodiment of the present invention.

FIG. 13 is a diagram illustrating a case of increasing the number ofcharging power receivers according to an embodiment of the presentinvention.

FIG. 14 is a flowchart of a shared mode protocol of a power transmitteraccording to an embodiment of the present invention.

FIG. 15 is a flowchart of a shared mode protocol of a power receiveraccording to an embodiment of the present invention.

DETAILED DESCRIPTION OF THE EMBODIMENTS

Terms used in this specification are common terms which are now widelyused by taking into consideration functions in this specification, butthe terms may be changed depending on an intention of those skilled inthe art, a use practice, or the appearance of a new technology.Furthermore, in a specific case, some terms have been randomly selectedby the applicant. In this case, the meaning of a corresponding term isdescribed in a corresponding part of a corresponding embodiment.Accordingly, the terms used in this specification should not beunderstood simply based on their names, but should be understood basedon their substantial meanings and contents over this specification.

Furthermore, although embodiments of the present invention are describedin detail with reference to the accompanying drawings and contentsdescribed in the drawings, the present invention is not limited to orrestricted by the embodiments.

Hereinafter, some embodiments of the present invention are described indetail with reference to the accompanying drawings.

For the standardization of wireless power transmitter/receivers,Wireless Power Consortium (WPC) standardizes technologies related towireless power transmission/reception.

A recently developed wireless charging system may support thetransmission/reception of low power of about 5 W. In this case, there isa problem in that a charging time is long and efficiency is low in sucha low power charging method because the size of a mobile device and thecapacity of a battery are recently increased. Accordingly, a wirelesscharging system supporting the transmission/reception of middle power ofabout 15 W˜20 W is developed. Furthermore, in order to improve chargingefficiency, a wireless charging system to which a resonant method forsimultaneously charging a plurality of electronic devices has been addedis developed.

An embodiment of the present invention relates to a wireless chargingsystem to which the resonant method has been added and proposes awireless charging transmitter/receiver using the resonant method, whichis compatible with a wireless charging transmitter/receiver using anelectromagnetic induction method supporting low power/middle power.

A wireless power transmitter and wireless power receiver of a resonanttype proposed by an embodiment of the present invention and a wirelesscharging method and a communication protocol using the wireless powertransmitter and wireless power receiver are described below.Hereinafter, a wireless power transmitter may be abbreviated as a powertransmitter or a transmitter, and a wireless power receiver may beabbreviated as a power receiver or a receiver.

FIG. 1 shows an embodiment of various electronic devices into which awireless charging system is introduced.

FIG. 1 shows that electronic devices are classified depending on anamount of power that is transmitted and received in a wireless chargingsystem.

Referring to FIG. 1, a small power (about 5 W or less or about 20 W orless) wireless charging method may be applied to wearable devices, suchas a smart watch, smart glass, a head mounted display (HMD), and a smartring, and mobile electronic devices (or portable electronic devices),such as an earphone, a remote controller, a smart phone, a PDA, and atablet PC. A middle power (about 50 W or less or about 200 W or less)wireless charging method may be applied to middle/small-sized homeappliances, such as a notebook computer, a robot clearer, TV, audioequipment, and a monitor. A large power (about 2 kW or less or 22 kW orless) wireless charging method may be applied to kitchen equipment, suchas a mixer, a microwave, and an electric rice cooker, and personalmobile devices (or electronic devices/mobile means), such as a wheelchair, an electric kickboard, an electric bicycle, and an electricvehicle.

Each of the aforementioned electronic devices/mobile means (or shown inFIG. 1) may include a wireless power receiver to be described later.Accordingly, the aforementioned electronic devices/mobile means may bewirelessly charged with power received from a wireless powertransmitter.

Hereinafter, a mobile device to which the small wireless charging methodis applied is chiefly described for convenience of description, but thisis only an embodiment. A wireless charging method in accordance with anembodiment of the present invention may be applied to the aforementionedvarious electronic devices.

FIG. 2 is a block diagram of a wireless power transmission/receptionsystem in accordance with an embodiment of the present invention.

Referring to FIG. 2, a wireless power transmission/reception system 2000includes a mobile device 2010 configured to wirelessly receive power anda base station 2020 configured to wirelessly transfer (or transmit)power. Hereinafter, the mobile device may also be called a “powerreceiver product”, and the base station may also be called a “powertransmitter product.”

The mobile device 2010 includes a power receiver 2011 for wirelesslyreceiving power through a secondary coil and a load 2012 for receivingpower received by the power receiver 2011, storing the received power,and supplying the stored power to a device.

The power receiver 2011 may include a power pick-up unit 2013 and acommunications & control unit 2014. The power pick-up unit 2013 mayreceive a wireless power signal through the secondary coil and convertthe received signal into electric energy. The communications & controlunit 2014 may control the transmission/reception of a power signal (orpower).

The base station 2020 is a device for providing inductive power orresonant power, and may include at least one power transmitter 2021 or asystem unit 2024.

The power transmitter 2021 may send inductive power or resonant powerand control such transmission. The power transmitter 2021 may include apower conversion unit 2022 configured to convert electric energy into apower signal by generating a magnetic field through a primary coil(s)and a communications & control unit 2023 configured to controlcommunication and power transfer with the power receiver 2011 so thatpower of a proper level is transferred. The system unit 2024 may performcontrol of other operations of the base station 2020, such as inputpower provisioning, control of a plurality of power transmitters, andcontrol of a user interface.

The power transmitter 2021 may control transmission power by controllingan operating point. The controlled operating point may correspond to acombination of a frequency (or phase), a duty cycle, a duty ratio, andvoltage amplitude. The power transmitter 2021 may control transmissionpower by controlling at least one of a frequency (or phase), a dutycycle, a duty ratio, or voltage amplitude.

Furthermore, the power transmitter 2021 may supply constant power, andthe power receiver 2011 may control reception power by controlling aresonant frequency.

Hereinafter, a coil or a coil unit may also be called a coil assembly, acoil cell, or a cell which includes a coil and at least one elementclose to the coil.

FIG. 3 is a block diagram of the power transmitter product in accordancewith an embodiment of the present invention.

Referring to FIG. 3, the power transmitter product PTP may include atleast one of a cover configured to cover a coil assembly 3020, a poweradapter 3070 configured to supply power to a power transmitter PTx, thepower transmitter PTx configured to send (or transmit) wireless power,or a user interface 3060 configured to provide information related tothe progress of power transfer and other related information. Inparticular, the user interface 3060 may be optionally included in thepower transmitter product PTP or may be included as another userinterface of the power transmitter product PTP.

The power transmitter PTx may include at least one of the coil assembly3020, a tank circuit (or impedance matching circuit) 3040, an inverter3080, a communication unit 3030, or a control unit 3050.

The coil assembly 3020 may include at least one primary coil forgenerating a magnetic field.

The tank circuit 3040 may provide impedance matching between theinverter 3080 and the primary coil(s). The tank circuit 3040 maygenerate resonance in a frequency suitable for boosting the current ofthe primary coil. In a multi-coil PTx, the tank circuit 3040 may furtherinclude a multiplexer for routing a signal from the inverter 3080 to asubset of the primary coils. The tank circuit 3040 may also be called animpedance matching circuit.

The inverter 3080 may change DC input into an AC signal. The inverter3080 may be driven as a half-bridge or a full-bridge so that itgenerates a pulse wave of an adjustable frequency and a duty cycle.Furthermore, the inverter 3080 may include a plurality of stages forcontrolling an input voltage level.

The communication unit 3030 may perform communication with a powerreceiver. The power receiver performs load modulation in order tocommunicate a request and information for the power transmitter PTx.Accordingly, the power transmitter PTx may monitor the amplitude and/orphase of the current and/or voltage of the primary coil in order todemodulate data transmitted by a power receiver using the communicationunit 3030. Furthermore, the power transmitter PTx may control outputpower so that data is transmitted through the communication unit 3030using a frequency shift keying (FSK) method. To this end, the powertransmitter PTx may further include a current sensor. In this case, thepower transmitter PTx may discover a power receiver by detecting achange in the current of the primary coil and detect data transmitted bythe discovered power receiver.

The control unit 3050 may control the communication and power transferof the power transmitter PTx. The control unit 3050 may control powertransfer by controlling the aforementioned operating point. Theoperating point may correspond to at least one of an operatingfrequency, a duty cycle, a duty ratio, or an input voltage, for example.

The elements of the power transmitter product PTP may be provided asseparate units/elements/chipsets or may be provided as a singleunit/element/chipset as shown in FIG. 1. For example, the communicationunit and the control unit may be provided as separate elements/chipsetsor may be provided as a single element/chipset as shown in FIG. 1.Furthermore, the elements of the power transmitter product PTP may beoptionally included, or a new element(s) may be added to the powertransmitter product PTP.

FIG. 4 is a block diagram of a power receiver product in accordance withan embodiment of the present invention.

Referring to FIG. 4, the power receiver product PRP may include at leastone of a user interface 4020 configured to provide information about theprogress of power reception and other related information, a powerreceiver PRx configured to receive wireless power, a load circuit 4080,or a base 4010 configured to support or cover a coil assembly 4070. Inparticular, the user interface 4020 may be optionally included in thepower receiver product PRP or may be included as another user interfaceof the power receiver product PRP.

The power receiver PRx may include at least one of a power converter4050, a tank circuit (or impedance matching circuit) 4060, the coilassembly 4070, a communication unit 4040, or a control unit 4030.

The power converter 4050 may convert AC power, received from a secondarycoil, into a voltage and current suitable for the load circuit 4080. Thepower converter 4050 may include a rectifier. The power converter 4050may further adapt reflected impedance of the power receiver PRx.

The tank circuit 4060 may provide impedance matching between thesecondary coil and a combination of the power converter 4050 and theload circuit 4080. In an embodiment, the tank circuit 4060 may generateresonance of about 100 kHz which may enhance power transfer.

The coil assembly 4070 includes at least one secondary coil and mayfurther include an element for shielding the metal part of a receiveragainst a magnetic field.

The communication unit 4040 may perform load modulation in order tocommunicate a request and other information for the power transmitterPTx. To this end, the power receiver PRx may switch a resistor orcapacitor on or off so that reflected impedance is changed.

The control unit 4030 may control reception (or received) power. To thisend, the control unit 4030 may determine/calculate a difference betweenthe actual operating point of the power receiver PRx and a requiredoperating point. Furthermore, the control unit 4030 may control/reduce adifference an actual operating point and a required operating point bymaking a request to control reflected impedance and/or the operatingpoint of the power transmitter PTx. If such a difference is minimized,power can be optimally received.

The elements of the power transmitter product PTP may be provided asseparate units/elements/chipsets or may be provided as a singleunit/element/chipset as shown in FIG. 1. For example, the communicationunit and the control unit may be provided as separate elements/chipsetsor may be provided as a single element/chipset as shown in FIG. 1.Furthermore, the elements of the power transmitted product PTP may beoptionally included, or a new element(s) may be added the powertransmitter product PTP.

FIG. 5 is a diagram illustrating an operating mode of a wireless powertransmitting/receiving system according to an embodiment of the presentinvention.

A power transmitter may operate in a shared mode and/or an exclusivemode.

In a shared mode, one power transmitter simultaneously serves aplurality of power receivers (i.e., may provide power to a plurality ofpower receivers). A shared mode protocol simultaneously managesinformation exchange between a power transmitter and at least one powerreceiver in a shared mode.

The power transmitter and the power receiver optionally support a sharedmode. That is, a shared mode may be optionally supported by the powertransmitter and the power receiver. Therefore, when the powertransmitter/receiver supports a shared mode, it may be necessary tonotify this to another party power transmitter/receiver. In the presentinvention, a method of notifying this using a configuration packet (CFG)is suggested, and a detailed description related thereto will bedescribed in detail hereinafter in relation to FIGS. 11 to 14.

In an exclusive mode, the power transmitter serves one power receiver atone time (i.e., provides power to one power receiver at one time). Anexclusive mode protocol manages information exchange between the powertransmitter and the power receiver in an exclusive mode. The powertransmitter and the power receiver mandatorily support an exclusivemode. That is, an exclusive mode may be mandatorily supported by thepower transmitter and the power receiver.

In an exclusive mode, the power receiver has the entire control right inpower transmission. In other words, the power receiver may control toincrease or reduce a power amount (or amount of magnetic power) beingtransmitted by the power transmitter. For this, a communication protocolbetween the power transmitter and the power receiver provides a feedbackloop for enabling the power receiver to control to appropriatelyincrease or reduce a current amount flowing through a primary coil ofthe power transmitter. For feedback to the power transmitter, the powerreceiver may use a temperature, a voltage, a current value, or aspecific sensor included in a power receiving equipment.

In a shared mode, the power transmitter may control a power amount (oramount of magnetic power) such that each power receiver receiving powerfrom the power transmitter shares power. The power receiver mayappropriately adjust impedance thereof to change a power amountreceiving from a magnetic field. When the power receiver may not (nolonger) adjust impedance thereof, the power receiver may control (orwarn) to increase or reduce a power amount being transmitted by thepower transmitter. For this, a communication protocol between the powertransmitter and the power receiver may provide a communication mechanismthat synchronizes the control of the power transmitter by each powerreceiver. In preparation for a collision of the control, the controlthat increases a receiving power amount may have a priority higher thanthe control that reduces a receiving power amount.

A shared mode may be referred to as a resonant mode, and an exclusivemode may be referred to as an induction mode. A wireless powertransmitting/receiving system may transmit/receive resonant power in ashared mode and may transmit/receive induction power in an exclusivemode.

Hereinafter, first, a power transfer method of a powertransmitter/receiver operating in an exclusive mode will be described.However, a method described in an exclusive mode or at least one ofsteps included in the method may be optionally applied to a shared mode.

FIG. 6 is a state diagram of a wireless power transmitter in anexclusive mode.

Referring to FIG. 6, in an exclusive mode, wireless charge may beperformed through four phases. The four phases include a selectionphase, a ping phase, an identification & configuration phase, and apower transfer phase.

At the selection phase, the power transmitter monitorscontact/separation of an object with/from an interface surface providedat the transmitter. For this reason, the power transmitter may usevarious means. When at least one object is found, the power transmittermay attempt to search for an accurate position of the found object(particularly, when the power transmitter supports free positioning).Further, the power transmitter may distinguish whether the found objectis a power receiver or a simple external object (key, coin). Further,the power transmitter may attempt to select a power receiver for powertransmission.

When sufficient information for performing the above-describedoperations does not exist, the power transmitter may repeatedly performa ping phase and an identification & configuration phase (whenever thisphase is performed, different primary coils may be selected), and afterrelated information is collected, the power transmitter may return to aselection phase.

When the power transmitter selects a primary coil for transmitting powerto the power receiver, the power transmitter may enter to the pingphase. In contrast, when the power transmitter does not select a powerreceiver for power transmission and/or when the power transmitter doesnot provide power to the power receiver because of excess of apredetermined time, the power transmitter may operate in a stand-bymode.

At the ping phase, the power transmitter may perform digital ping andstand by a response of the power receiver. The digital ping representsapplication/transmission of a power signal for detecting and identifyingthe power receiver. When the power transmitter finds the power receiver,the power transmitter may enlarge digital ping and proceed to theidentification & configuration phase.

At the identification & configuration phase, the power transmitter mayidentify the selected power receiver and acquire configurationinformation of the power receiver such as a maximum power amount. Inother words, the power transmitter may receiveidentification/configuration information, acquire information about thepower receiver, and create a power transfer contract using theinformation. The power transfer contract may include a limitation of aplurality of parameters that characterize power transfer at a subsequentpower transfer phase.

At the power transfer phase, the power transmitter provides power to thepower receiver by wireless. The power transmitter may receive controldata of transmitted power from the power receiver to adjust a primarycell current, thereby controlling power transfer. Further, the powertransmitter may monitor parameters included in a power transfercontract. While transferring power, when a limitation of parametersaccording to a power transfer contract is violated, the powertransmitter may stop power transfer and advance to a selection phase.

A state diagram described in this drawing is a state diagram describedbased on a low power mode, and in an intermediate power mode, a newphase (e.g., calibration phase, negotiation phase, and renegotiationphase) may be added or some phases may be deleted.

FIG. 7 is a diagram illustrating a power transfer control method in anexclusive mode.

In FIG. 7, the power transmitter and the power receiver each may includea power conversion unit and a power pickup unit, as shown in FIG. 1.

At the power transfer phase of the exclusive mode, the power transmitterand the power receiver may perform communication together with powertransmission and reception to control an amount of transferred power.The power receiver may select a specific control point and operate witha specific control point. The control point represents a combination ofa voltage and a current provided from an output of the power receiverwhen power transfer is performed.

In more detail, the power receiver may select a desired control point (adesired output current/voltage, a temperature of a specific position ofa mobile device) and additionally determine a currently operating actualcontrol point. The power receiver may calculate a control error valueusing a desired control point and an actual control point and transmitthe control error value as a control error packet to the powertransmitter. The control error packet is transmitted/received at apredetermined time interval at the power transfer phase, and as anembodiment, when reducing a current of the power transmitter, the powerreceiver may set a control error value to the negative number andtransmit the control error value, and when increasing a current of thepower transmitter, the power receiver may set a control error value tothe positive number and transmit the control error value.

In order to determine a new primary cell current, the power transmittermay use a received control error value and an actual primary cellcurrent. After a system is stabilized by communication of a controlerror packet, the power transmitter may control an actual primary cellcurrent with a new primary cell current. In this case, the powertransmitter may operate at a new operation point (amplitude, frequency,and duty cycle applied to a primary cell).

In a resonant mode to describe hereinafter, the power transmitter mayoperate with a method different from a method in an exclusive mode. In aresonant mode, one power transmitter should be able to simultaneouslyserve a plurality of power receivers. However, as in the foregoingexclusive mode, when power transfer is controlled, transferred power iscontrolled by communication with one power receiver and thus it may bedifficult to control power transfer to additional power receivers.Therefore, in a resonant mode, the power transmitter may commonlytransfer basic power, and the power receiver may control a resonantfrequency thereof to control a receiving power amount. However, even inoperation in such a resonant mode, a method described in relation toFIGS. 6 and 7 is not completely excluded, and the control of additionaltransmission power may be performed with a method of FIGS. 6 and 7.

FIG. 8 shows the state diagram of the power receiver in shared mode.Hereinafter, the power receiver is chiefly described, but a descriptionregarding the state to be described later may be identically (orsimilarly) applied to the power transmitter.

In shared mode, the power receiver may be in a selection state, anintroduction state, a configuration state, a negotiation state, or apower transfer state. The selection state may correspond to a selectionphase, the introduction state may correspond to an introduction phase,the configuration state may correspond to a configuration phase, thenegotiation status may correspond to a negotiation phase, and the powertransfer state may correspond to a power transfer phase.

The selection phase corresponds to a selection phase in which inexclusive mode, the power transmitter monitors the contact/detachment ofan object with respect to a surface of the interface included in thepower transmitter. The selection phase in shared mode may be omitted.Accordingly, the power receiver may perform the remaining four phases.When detecting the presence of frequency shift keying (FSK) in a powersignal prior to wake-up time-out, the power receiver may immediatelyperform the introduction phase after the selection phase.

In the introduction phase, the power receiver may request a free slot inwhich a control information (CI) packet to be used in next phases (e.g.,the configuration phase, the negotiation phase, or the power transferphase) will be transmitted. To this end, the power receiver sends aninitial CI packet. If the power transmitter makes a response as ACK, thepower receiver may enter the configuration phase. If the powertransmitter makes a response as NACK, another power receiver may haveperformed the configuration phase or the negotiation phase. In thiscase, the power receiver may request a free slot from the powertransmitter again. When the power receiver receives ACK from the powertransmitter, the power receiver may determine the location of its ownprivate slot in a frame and then send a CI packet using the slot at thedetermined location.

In the configuration phase, the power transmitter may provide a seriesof locked slots for the exclusive use of the power receiver. In thiscase, the power receiver may perform the configuration phase without acollision. The power receiver may send two identification data packetsIDHI and IDLO, a version information packet VSN, and optionally at leastone proprietary data packet and a configuration packet CFG using thelocked slots. When the configuration phase is completed, the powerreceiver may enter the negotiation phase.

In the negotiation phase, the power transmitter may continue to supplylocked slots for the exclusive use of the power receiver. In this case,the power receiver may perform the negotiation phase without acollision. The power receiver may send a negotiation data packet(including a specific request SRQ) and a general request (GRQ)) and/orat least one optional proprietary data packet using the locked slots.Furthermore, the power receiver may terminate the negotiation phase bysending an SRQ/end-negotiation (en) packet. When the negotiation phaseis terminated, the power transmitter enters the power transfer phase,and the power transmitter stops the supply of locked slots.

In the power transfer phase, the power receiver sends a CI packet usinga free slot determined in the introduction phase and receives power. Thepower receiver may include a regulator circuit. The regulator circuitmay be included in the aforementioned communications & control unit. Thepower receiver may self-regulate reflected impedance of the powerreceiver through the regulator circuit. That is, the power receiver mayregulate reflected impedance using the regulator circuit in order totransfer the amount of power necessary for an external load, to preventexcessive power from being received, or to prevent overheating. Inshared mode, the power transmitter may not regulate transmission powerin response to a received CI packet in operating mode. In this case, thepower receiver may control the regulator circuit in order to prevent anover-voltage situation.

In a shared mode, the power transmitter should manage informationexchange with at least one power receiver. For this reason, the powertransmitter provides a structure for communication with the powerreceiver, and such a structure will be described in detail hereinafterin relation to a communication frame structure of FIG. 9.

FIG. 9 is a diagram illustrating a frame structure for datacommunication.

Referring to FIG. 9, the power transmitter provides a structure thatprovides a sequence of time slots in which each power receiver maytransmit data packet. A sync pattern is provided between slots. The syncpattern performs a function of separating slots and optimizingcommunication of the power receiver. Particularly, the sync pattern mayprovide information for collision resolution and guaranteed latency tothe power receiver.

A shared mode protocol may use two kinds of frames, i.e., a slottedframe (see FIG. 9A) and a free-format frame (see FIG. 9B). When thepower receiver transmits a short data packet to the power transmitter,the slotted frame may be used. The free-format frame may be used for anobject such as transmission of a larger data packet in a bi-directionand coil selection in a multi coil transmitter.

All frames are started at a sync pattern and a measurement slot, and themeasurement slot may be used for measurement of transmission power andreception power. As an embodiment, 9 slots may be included in oneslotted frame. In the free-format frame, after a sync pattern and ameasurement frame, there is no specific form limitation. A start bit(information) of the sync pattern may represent the start of the frame.

FIG. 10 is a diagram illustrating a format of a sync pattern accordingto an embodiment of the present invention.

Referring to FIG. 10, the sync pattern may include at least one of apreamble, a start bit, a response field, a type field, an info field,and a parity bit.

The preamble includes a sequence of bits set to ‘1’. The included bitnumber may be changed according to an operation frequency.

The start bit may be set to ‘0(ZERO)’.

The parity bit is a final bit of the sync pattern, and when bits set to1 and included in data fields included in the sync pattern are the evennumber, the parity bit may be set to 1, and in the other case (i.e.,when bits set to 1 and included in data fields included in the syncpattern are the odd number), the parity bit may be set to 0.

The response field may include a response of the power transmitter tocommunication using a preceding slot from the power receiver. ‘00’ mayrepresent that communication was not detected, ‘01’ may represent that acommunication error was detected, ‘10’ may represent not-acknowledge tocorrect reception of communication, and ‘11’ may represent acknowledgeto correct reception of communication.

When a sync pattern including a corresponding type field is a first syncpattern included in a frame, the type field may be set to ‘1’. Further,when a sync pattern including a corresponding type field is not a firstsync pattern included in the frame, the type field may be set to ‘0’.

The info field has different values and meanings according to a syncpattern representing in the sync field (or type field).

First, when the type field is ‘1’, the info field may represent that theframe is a slotted frame or a free-format frame. When the info fieldrepresents that the frame is a slotted frame, the info field may be setto ‘00’. Further, when the info field represents that the frame is afree-format frame, the info field may be set to ‘01’.

When the type field is ‘0’, the info field may represent that a nextslot is a slot allocated to a specific receiver, a locked slottemporarily provided to a specific receiver, or a free slot that can beused by any receiver. When the info field represents that a next slot isa slot allocated to a specific receiver, the info field may be set to‘00’. Further, when the info field represents that a next slot is alocked slot temporarily provided to a specific receiver, the info fieldmay be set to ‘01’. Further, when the info field represents that a nextslot is a free slot that can be used by any receiver, the info field maybe set to ‘10’.

As described above, a shared mode (or a shared mode protocol) may beoptionally supported by a power transmitter/receiver. Therefore, it isnecessary that the power transmitter that supports a shared mode (or ashared mode protocol) knows whether the power receiver to transmit powersupports a shared mode (or a shared mode protocol). For example, whilethe power transmitter transmits power to the first power receiver, itmay be assumed that a new second power receiver is introduced into acharge area (or a wireless chargeable area). In this case, when a newlyintroduced power receiver may support a shared mode (or a shared modeprotocol), the power transmitter may simultaneously transmit power to aplurality of power receivers (first and second power receiver)positioned within a charge area and thus the power transmitter shouldknow whether the second power receiver supports a shared mode (or ashared mode protocol).

Therefore, hereinafter, a new method is suggested that notifies whethersupport of a shared mode (or a shared mode protocol) by includinginformation representing whether support of a shared mode in aconfiguration packet transmitted and received at an identification &configuration phase (or configuration phase).

FIG. 11 is a diagram illustrating a configuration packet according to afirst embodiment of the present invention. In more detail, FIG. 11 is adiagram illustrating a format of a message payload included in aconfiguration packet according to a first embodiment of the presentinvention.

Referring to FIG. 11, the configuration packet may include a MaximumReceived Power field, a Power Class field, a Count field, a ZERO field,a Reserved field, a Prop field, a Window Offset field, a Window Sizefield, an Operation Mode field, a Neg field, a Polarity (Pol) field, anda Depth field.

The Count field includes the number of selective data packetstransmitted by a power receiver before a configuration packet. Thisfield may be used only in an exclusive mode.

The Depth field may include a scaling factor calculated to 2 Depth for arequested FSK modulation depth. This field may be used only in anexclusive mode.

The Maximum Received Power field may include a received highest powervalue (expect to report in the power packet received by the powerreceiver) in a unit of 0.5 W.

The Operation Mode field (1 bit) may instruct whether the power receiverthat transmits a configuration packet supports a shared mode (or ashared mode protocol). For example, when the Operation Mode field is setto ‘0’, the Operation Mode field may instruct that the power receiversupports an exclusive mode (one-to-one wireless charge mode)(or anexclusive mode protocol). Alternatively, when the Operation Mode fieldis set to ‘1’, the Operation Mode field may instruct that the powerreceiver supports a shared mode (one-to-N wireless charge mode) inaddition to an exclusive mode (in addition to an exclusive mode).

When requesting the start of a negotiation phase in an exclusive mode tothe power transmitter, the Neg field may be set to ‘1’. In other case,the Neg field may be set to ‘0’. This field may be used only in anexclusive mode.

When requesting that the power transmitter uses the negative FSKpolarity, the Polarity (Pol) field may be set to ‘1’ (i.e., fop<fmod).In contrast, when requesting that the power transmitter uses thenegative FSK polarity, the Polarity (Pol) field may be set to ‘1’. Thisfield may be used only in an exclusive mode.

The power class field may be set to ‘00’.

When requesting to control power transmission to the power transmitterusing a proprietary method instead of proportional-integral-differential(PID) algorithm, the prop field may be set to ‘1’, and in other case,the prop field may be set to ‘0’. This field may be used only in anexclusive mode.

The reserved field may be set to ‘0’.

The window offset field may include a time interval from the end of awindow for averaging received power to a start bit of a received powerpacket in a unit of 4 ms. This field may be used only in an exclusivemode.

The window size field may include a size of a window used for averagingpower received by the power receiver in a unit of 4 ms. This field maybe used only in an exclusive mode.

A power transmitter operating in a shared mode may disregard fields usedonly in an exclusive mode among the above-described fields.Alternatively, a power transmitter that supports a shared mode protocolmay disregard fields used only in an exclusive mode protocol among theabove-described fields.

In the first embodiment, an example has been described that defines abit (B4, b3) of a specific position of the configuration packet to anoperation mode field and that directly instructs whether support of ashared mode, but the present invention is not limited thereto and atleast one of reserved fields included in the configuration packet may beused as a field that instructs whether support of a shared mode (or ashared mode protocol).

Further, the configuration packet is not limited to the firstembodiment, at least one of the above-described fields may beselectively included, and a new field may be additionally included.

FIG. 12 is a diagram illustrating a configuration packet according to asecond embodiment of the present invention. In more detail, FIG. 12 is adiagram illustrating a format of a message payload included in aconfiguration packet according to a second embodiment of the presentinvention. A description of the remaining fields, except for a sharedmode field among fields included in a configuration packet of thisdrawing is the same as that of FIG. 11 and therefore a detaileddescription thereof will be omitted.

Referring to FIG. 12, a configuration packet may include a shared modefield (1 bit) representing whether a shared mode (or a shared modeprotocol) is supported. The shared mode field may instruct whether apower receiver that transmits a configuration packet supports a sharedmode (or a shared mode protocol). For example, when the shared modefield is set to ‘0’, the shared mode field may instruct that the powerreceiver does not support a shared mode (or a shared mode protocol).Alternatively, when the shared mode field is set to 1′, the shared modefield may instruct that the power receiver supports a shared mode(one-to-N wireless charge mode)(or a shared mode protocol) (in additionto an exclusive mode).

In the second embodiment, an embodiment has been described that definesa bit (B4, b3) of a specific position of the configuration packet to ashared mode field and that directly instructs whether a shared mode (ora shared mode protocol) is supported and the present invention is notlimited thereto, and at least one of reserved fields included in theconfiguration packet may be used as a field that instructs whether ashared mode (or a shared mode protocol) is supported.

Further, the configuration packet is not limited to the secondembodiment and may selectively include at least one of theabove-described fields and additionally include a new field.

In this way, the power receiver may notify the power transmitter whethera shared mode (or a shared mode protocol) is supported through theconfiguration packet at identification & configuration phase (orconfiguration phase). When a new power receiver is introduced into acharge area of a multi coil power transmitter while charging anotherpower receiver, the present embodiment may be more efficiently used andthis will be described hereinafter in relation to FIGS. 13 and 14.

In this specification, for convenience of description, an operation modefield of the first embodiment or a shared mode field of the secondembodiment may be referred to as a ‘mode field’, ‘shared field’ or‘shared bit’.

FIG. 13 is a diagram illustrating a case of increasing the number ofcharging power receivers according to an embodiment of the presentinvention.

Referring to FIG. 13, while a power transmitter PTx transmits power to afirst power receiver PRx1 positioned within a charge area 13010, it maybe assumed that a new second power receiver PRx2 is introduced into thecharge area 13010. In this case, the power transmitter PTx may be apower transmitter including multi coils. In this case, as a second powerreceiver Rx2 transmits a configuration packet to the power transmitterat the identification & configuration phase (or configuration phase)according to a second embodiment, the power transmitter PTx may detectthe second power receiver PRx2 without stop of power transmission to thefirst power receiver PRx1.

In more detail, when the power transmitter PTx detects a new object, inorder to detect whether a corresponding object is a power receiver, thepower transmitter PTx may use a free-format frame. Further, when acorresponding object is a power receiver, in order to additionallydetect an optimal coil for power transmission, the power transmitter PTxmay use a free-format frame.

For this reason, immediately after a measurement slot, the powertransmitter PTx may activate at least one embedded primary coil andstand by reception of a data packet from the second power receiver PRx2.Because the second power receiver PRx2 does not detect FSK in a powersignal, the second power receiver PRx2 may start in an exclusive modeand transmit a Signal Strength (SS) packet to the power transmitter PTx.The power transmitter PTx, having received the SS packet, may shut downthe second power receiver PRx2. The process may be repeatedly performedfor a free-format frame of (sets of) different primary coil(s).

With such a method, the power transmitter PTx may determine (or select)a primary coil most appropriate for power transmission. Thereafter, thepower transmitter PTx may determine whether the second power receiverPRx2 supports a shared mode protocol using a primary coil(s) setdetermined as appropriate for power transmission. For this reason, thepower transmitter PTx may restart the second power receiver PRx2 (stillin an exclusive mode, at a next free-format frame, if possible) andreceive a configuration packet from the second power receiver PRx2. Inthis case, the configuration packet may follow a format of the first orsecond embodiment.

The power transmitter PTx may recognize (or determine) whether thesecond power receiver PRx2 supports a shared mode through a field(operation mode field in the first embodiment and shared mode field inthe second embodiment) that instructs whether support of a shared modeincluded in a configuration packet received from the second powerreceiver PRx2.

When it is recognized (or determined) that the second power receiverPRx2 supports a shared mode, the power transmitter PTx may start thesecond power receiver PRx2 at a start time point of a next slotted frame(i.e., may transmit power to the second power receiver). In this case,the second power receiver PRx2 may detect FSK in a power signal andfollow a shared mode protocol (i.e., may operate in a shared mode) inorder to participate in power transmission (or reception) together withthe first power receiver PRx1.

In contrast, when it is recognized (or determined) that the second powerreceiver PRx2 does not support a shared mode, the power transmitter PTxmay not transmit power to the second power receiver PRx2 (or may powerdown the second power receiver PRx2) until the power transmitter PTx isprepared to serve the second power receiver PRx2 in an exclusive mode.

FIG. 14 is a flowchart of a shared mode protocol of a power transmitteraccording to an embodiment of the present invention. A descriptiondescribed with reference to FIG. 13 may be equally applied to adescription related to this flowchart and a repeated description may beomitted.

First, while transmitting power to a first power receiver, the powertransmitter may detect a second power receiver (S14010). For example,the power transmitter may detect a second power receiver newlyintroduced to a corresponding charge area while transmitting power tothe first power receiver positioned in a charge area.

Thereafter, the power transmitter may determine a primary coilappropriate for power transmission (S14020). In more detail, the powertransmitter may determine at least one primary coil most appropriate forpower transmission to the second power receiver. For this reason, thepower transmitter may perform a process of sequentially activating atleast one primary coil and receiving an SS packet from the second powerreceiver for a free-format frame.

Thereafter, the power transmitter may determine (or recognize/judge)whether the second power receiver supports a shared mode protocol usingat least one primary coil determined at a previous step (S14030). Inthis case, the power transmitter may receive a configuration packet(using the primary coil) from the second power receiver, and a modefield included in the configuration packet instructs whether the secondpower receiver supports a shared mode protocol. Therefore, the powertransmitter determines whether the second power receiver supports ashared mode protocol through a mode field of the received configurationpacket.

Thereafter, when the second power receiver supports a shared modeprotocol, the power transmitter may simultaneously transmit power to thefirst and second power receivers according to a shared mode protocol(S14040).

Although not shown in this flowchart, when the second power receiverdoes not support a shared mode protocol, the power transmitter may nottransmit power to the second power receiver until the power transmitteris prepared to serve the second power receiver in an exclusive mode.

FIG. 15 is a flowchart of a shared mode protocol of a power receiveraccording to an embodiment of the present invention. This flowchartcorresponds to that of FIG. 14, and a description described withreference to FIGS. 13 and 14 may be equally applied to that of FIG. 15and a repeated description may be omitted.

First, the power receiver (e.g., the second power receiver) may bedetected by a power transmitter transmitting power to another powerreceiver (e.g., the first power receiver) (S15010).

Thereafter, the power receiver may transmit a configuration packet tothe power transmitter (S15020). In more detail, the power receiver maygenerate a configuration packet representing whether the power receiversupports a shared mode protocol and transmit the configuration packet tothe power transmitter. Particularly, a mode field of the configurationpacket may instruct whether the power receiver supports a shared modeprotocol, and when a mode field is set to 1′, the mode field instructsthat the power receiver supports the shared mode protocol, and when amode field is set to ‘0’, the mode field instructs that the powerreceiver does not support a shared mode protocol.

Thereafter, when the power receiver supports a shared mode protocol, thepower receiver may detect FSK in a power signal and participate in powertransmission (or reception) of the power transmitter together withanother power receiver according to a shared mode protocol (S15030).

Although not shown in this flowchart, when the power receiver does notsupport a shared mode protocol, the power receiver may not receive poweruntil the power transmitter is prepared to serve the corresponding powerreceiver in an exclusive mode.

In this specification, a shared mode protocol and a method ofinstructing whether support of a shared mode protocol have beendescribed.

According to the present invention, while a power transmitter transmitspower, even if a new power receiver participates in charge, the powertransmitter can let the new power receiver be participated in powertransmission effectively without disturbing power transmission to analready charging power receiver. Further, according to the presentinvention, a power receiver operating in an exclusive mode among aplurality of power receivers operating in a shared mode can be detected.

The drawings have been divided and described for convenience ofdescription, but the embodiments described with reference to thedrawings may be merged and designed to implement new embodiments.Furthermore, the display device is not limited and applied to theconfigurations and methods of the aforemtioned embodiments, but some orall of the embodiments may be selectively combined and configured sothat the embodiments are modified in various ways.

Furthermore, although some embodiments of this specification have beenillustrated and described, this specification is not limited to theaforementioned specific embodiments and may be modified in various waysby those skilled in the art to which this specification pertains withoutdeparting from the gist of this specification claimed in the claims. Themodified embodiments should not be individually interpreted from thetechnical spirit or prospect of this specification.

Various embodiments have been described in a best mode for executing thepresent invention.

The present invention may be applied to various wireless chargetechnologies.

What is claimed is:
 1. A method in which a power transmitter comprisingmulti coils transmits wireless power, the method comprising: detecting asecond power receiver while transmitting power to a first powerreceiver; determining at least one primary coil appropriate for powertransmission; determining whether the second power receiver supports ashared mode protocol using the determined at least one primary coil; andtransmitting, if the second power receiver supports a shared modeprotocol, power to the first and second power receivers according to theshared mode protocol, wherein the shared mode protocol is a protocolthat simultaneously manages information exchange between the powertransmitter and a plurality of power receivers, wherein the determiningof whether the second power receiver supports the shared mode protocolcomprises: receiving a configuration packet from the second powerreceiver; and determining whether the second power receiver supports theshared mode protocol through a mode field included in the configurationpacket.
 2. The method of claim 1, wherein the determining of whether thesecond power receiver supports the shared mode protocol through the modefield comprises: determining that the second power receiver supports theshared mode protocol when the mode field is set to ‘1’, and determiningthat the second power receiver does not support the shared mode protocolwhen the mode field is set to ‘0’.
 3. The method of claim 1, furthercomprising starting, if the second power receiver supports the sharedmode protocol, power transmission to the second power receiver at astart time point of a next slotted frame.
 4. The method of claim 1,further comprising not transmitting, if the second power receiver doesnot support the shared mode protocol, power to the second power receiveruntil the power transmitter is prepared to serve the second powerreceiver in an exclusive mode, wherein the exclusive mode is a mode thatserves one power receiver at one time.
 5. A method in which a powerreceiver receives wireless power, the method comprising: being detectedby a power transmitter transmitting power to another power receiver;transmitting a configuration packet indicating whether the powerreceiver supports a shared mode protocol to the power transmitter; anddetecting, if the power receiver supports the shared mode protocol,Frequency Shift Keying (FSK) in a power signal received from the powertransmitter and participating in power transmission of the powertransmitter together with the another power receiver according to theshared mode protocol, wherein the shared mode protocol is a protocolthat simultaneously manages information exchange between the powertransmitter and a plurality of power receivers, wherein a mode fieldincluded in the configuration packet indicates whether the powerreceiver supports the shared mode protocol.
 6. The method of claim 5,wherein: the mode field indicates that the power receiver supports theshared mode protocol, when the mode field is set to ‘1’, and the modefield indicates that the power receiver does not support the shared modeprotocol, when the mode field is set to ‘0’.
 7. The method of claim 5,further comprising starting, if the power receiver supports the sharedmode protocol, power reception from the power transmitter at a starttime point of a next slotted frame.
 8. The method of claim 5, furthercomprising not receiving, if the power receiver does not support theshared mode protocol, power from the power transmitter until the powertransmitter is prepared to serve the power receiver in an exclusivemode, wherein the exclusive mode is a mode in which the powertransmitter serves one power receiver at one time.
 9. A powertransmitter, comprising: a coil assembly comprising multi coils; aninverter configured to convert a DC signal to an AC signal; a tankcircuit configured to provide impedance matching; a communication unitconfigured to perform communication with a power receiver; and a controlunit configured to control power transfer, wherein the power transmitteris configured to: detect a second power receiver while transmittingpower to a first power receiver, determine at least one primary coilappropriate for power transmission, determine whether the second powerreceiver supports a shared mode protocol using the determined at leastone primary coil, and transmit power to the first and second powerreceivers according to the shared mode protocol when the second powerreceiver supports the shared mode protocol, wherein the shared modeprotocol is a protocol that simultaneously manages information exchangebetween the power transmitter and a plurality of power receivers, andwherein the power transmitter is further configured to receive aconfiguration packet from the second power receiver and determinewhether the second power receiver supports the shared mode protocolthrough a mode field included in the configuration packet.
 10. The powertransmitter of claim 9, wherein the power transmitter is furtherconfigured to: determine that the second power receiver supports theshared mode protocol when the mode field is set to ‘1’, and determinethat the second power receiver does not support the shared mode protocolwhen the mode field is set to ‘0’.
 11. The power transmitter of claim 9,wherein the power transmitter is further configured to start powertransmission to the second power receiver at a start time point of anext slotted frame when the second power receiver supports the sharedmode protocol.
 12. The power transmitter of claim 9, wherein the powertransmitter is further configured to do not transmit power to the secondpower receiver until the power transmitter is prepared to serve thesecond power receiver in an exclusive mode when the second powerreceiver does not support the shared mode, and wherein the exclusivemode is a mode that serves one power receiver at one time.
 13. A powerreceiver, comprising: a coil assembly comprising multi coils; a powerconverter configured to convert AC power to a voltage and a currentappropriate for a load circuit; a tank circuit configured to provideimpedance matching; a communication unit configured to performcommunication with a power receiver; and a control unit configured tocontrol power transfer, wherein the power receiver is configured to: bedetected by a power transmitter transmitting power to another powerreceiver, transmit a configuration packet indicating whether the powerreceiver supports a shared mode protocol to the power transmitter,detect Frequency Shift Keying (FSK) in a power signal received from thepower transmitter, and participate in power transmission of the powertransmitter together with the another power receiver according to theshared mode protocol, when the power receiver supports the shared modeprotocol, wherein the shared mode protocol is a protocol thatsimultaneously manages information exchange between the powertransmitter and a plurality of power receivers, and wherein a mode fieldincluded in the configuration packet indicates whether the powerreceiver supports the shared mode protocol.
 14. The power receiver ofclaim 13, wherein: the mode field indicates that the power receiversupports the shared mode protocol when the mode field is set to ‘1’, themode field indicates that the power receiver does not support the sharedmode protocol when the mode field is set to ‘0’.
 15. The power receiverof claim 13, wherein the power receiver is further configured to startpower reception from the power transmitter at a start time point of anext slotted frame when the power receiver supports the shared modeprotocol.
 16. The power receiver of claim 13, wherein the power receiveris further configured to do not receive power from the power transmitteruntil the power transmitter is prepared to serve the power receiver inan exclusive mode when the power receiver does not support the sharedmode protocol, and wherein the exclusive mode is a mode in which thepower transmitter serves one power receiver at one time.